1. Field of the Invention
The present invention relates to a piston for a setting tool and including a piston head having, in its combustion chamber-side end, an opening, and a hollow chamber adjoining the opening, and a stopper securable in the hollow chamber of the piston head with a solder seam for closing the opening.
2. Description of the Prior Art
In setting tools, a piston is displaceably supported in a hollow chamber. The piston is driven as a result of an explosive combustion of an appropriate fuel in the combustion chamber of a setting tool. With its setting direction side end, the piston engages a fastening element, which is located in a pin guide of the setting tool, and drives the fastening element into a, e.g., constructional component.
In combustion-engined setting tools, because of weight consideration, the piston is formed hollow and is closed with a stopper. The stopper is secured at the end of the piston hollow chamber by a soldering connection. In a conventional piston, it often happens that the stopper is not adequately centered. As a result, upon the soldering of the stopper in the hollow chamber, the solder seam is not uniform. The soldering connection is subjected to high loads as a result of action of high dynamic and thermal loads on the piston during the operation of the setting tool. The non-uniformity of the solder seam can lead to a premature breaking of the soldering connection and to the loss of the stopper.
Accordingly, an object of the present invention is to provide a setting tool piston in which the non-uniformity of the solder seam, which connects the stopper with the piston head, is prevented.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing centering means on the outer surface of the stopper.
The provision of the centering means on the circumference of the outer surface of the stopper, e.g., in form of knurling or a plurality of projections insures a concentric arrangement of the stopper in the hollow chamber of the piston head and, thereby, a formation of a soldering gap around the outer circumference of the stopper and which provides, at all of the points of the stopper circumference, similar geometrical conditions for a capillar effect between the piston head and the outer circumference of the stopper. The present invention noticeably reduces amount of rejects during manufacturing of hollow pistons. Further, the present invention increases the service life of the piston as in each case, a stable soldering connection can be achieved.
According to an advantageous embodiment of the present invention, the outer diameter of the centering means, which is formed e.g., as a knurling, is somewhat greater than the inner diameter of the hollow chamber of the piston in the stopper insertion region. This insures that the stopper cannot move during the assembly and the soldering process. The present invention ensures precise and quality manufacturing of the piston resulting in a quality end product.
According to the present invention, the stopper is provided with a solder repository, which can also be formed at the opening in the piston head or in the hollow chamber of the piston head. The solder repository prevents deposition of the excess solder, during the soldering process, on the finished, continuous end surface of the stopper which, otherwise, would have to be subjected to additional treatment. The elimination of the additional treatment of the end surface of the stopper after soldering reduces manufacturing costs.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiment, when read with reference to the accompanying drawings.